#include<iostream>
using namespace std;
double n;
int main()
{
	cin >> n;
	double l = -10000;
	double r = 10000;
	while (l + 1e-8 < r) {
		double mid = (l + r) * 1.0 / 2;
		if (mid * mid * mid <= n) {
			l = mid;
		}
		else {
			r = mid;
		}
	}
	cout << l << endl;
	return 0;
}